Chemically modified vegetable oil-based industrial fluid

ABSTRACT

Triglyceride oils having unsaturated fatty acid substituents are modified to convert sites of unsaturation to C-2 to C-10 diesters. The resulting derivatives are characterized by thermal and oxidative stability, have low temperature performance properties and are environmentally-friendly. They have utility as hydraulic fluids, lubricants, metal working fluids and other industrial fluids. The triglyceride oils are most easily prepared via epoxidized vegetable oils which are converted to the diesters in either a one- or two-step reaction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a novel chemically modified vegetableoil-based industrial fluid having superior performance properties and tomethods for its preparation.

2. Description of the Prior Art

Most of the lubricants currently in daily use originate from petroleumbase stocks that are toxic to environment, making it increasinglydifficult for safe and easy disposal. There has been a increasing demandfor “green”lubricants [Rhee, I., NLGI Spokesman, 60(5):28 (1996)] inrecent years due to concerns about loss of mineral oil-based lubricantsto the environment and increasingly strict government regulationscontrolling their use. Losses from accidental spillage andnon-recoverable usage can result in ground water contamination and posea threat to animal and plant life.

Vegetable oils such as rapeseed oil and high oleic varieties of otheroils are considered to be potential candidates to replace conventionalmineral oil-based lubricating oils and synthetic esters [Randles, S. J.et al.; J. Syn. Lubr., 9:145 1992); Asadauskas, S. et al.; Lub. Eng.,52:877 (1996)]. Vegetable oils are non-toxic, renewable resources andlower cost alternatives to synthetic fluids. The primary industrialapplication of vegetable oil use has been in the area of biodegradablehydraulic fluids. They have very low volatility due to high molecularweight of triacylglycerol molecule and narrow range of viscosity changewith temperature. The ester linkages deliver inherent lubricity andenable the oils to adhere to metal surfaces. Further, vegetable oilshave higher solubilizing capacity for contaminants and additives thanmineral base fluids.

The most serious disadvantage of vegetable oils is their poor oxidativestability [Becker, R. et al.; Lubr. Sci., 8:95 (1996); Gapinski, R. E.et al.; SAE Tech Pap. 941785, pages 1-9 (1994)], primarily due to thepresence, of bis allylic protons. These protons arc highly susceptibleto radical attack and subsequently undergo oxidative degradation to formpolar oxy compounds. This oxy-polymerization process ultimately resultsin insoluble deposit formation, and an increase in oil acidity andviscosity. Vegetable oils also show poor corrosion protection [Ohkawa,S. A. et al.; SAE Tech paper 951038, pages 55-63 (1995)], and thepresence of ester functionality render these oils susceptible tohydrolytic breakdown [Rodes, B. N., et al.; SAE Tech paper 952073, pages1-4 (1995)]. Therefore contamination with water in the form of emulsionmust be prevented at every stage. Low temperature studies have alsoshown that most vegetable oils undergo cloudiness, precipitation, poorflow and solidification at cold temperatures.

SUMMARY OF THE INVENTION

We have now discovered a novel class of chemically-modified vegetableoils and chemically-modified vegetable oil-based industrial fluids aswell as methods for producing them from triglyceride oils havingunsaturated fatty acid substituents. The resultant vegetable oilderivatives, having diester substitution at the sites of unsaturation,have utility in hydraulic fluids, lubricants, metal working fluids andthe like.

In accordance with this discovery, it is an object of this invention toprovide novel vegetable oil derivatives.

It is also an object of the invention to provideenvironmentally-friendly vegetable oil-based industrial fluids havingacceptable low temperature performance properties.

It is a specific object of this invention to provide vegetable oil-basedindustrial fluids having acceptable thermal and oxidative stability andlow temperature fluidity.

Another object of the invention is to introduce a new use for vegetableoils and to expand the market for an agricultural commodity.

A further object of the invention is produce industrial fluids thatreduce the demand on petroleum resources and that are biodegradable.

It is also an object of the invention to provide both a single-step anda two-step synthetic route for converting sites of unsaturation intriglyceride fatty esters to diester functionality.

Other objects and advantages of this invention will become readilyapparent from the ensuing description, dr

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1 is a graph comparing the percent of insoluble deposit of soybeanoil (⋄), epoxidized soybean oil (▭) and di-OHx-soybean oil (Δ) duringthin film micro-oxidation (TFMO) at 175° C. under air flow (20ml/minute).

DETAILED DESCRIPTION

The vegetable oil-based lubricants of the invention are prepared fromtriglycerides composed of fatty acid ester groups that collectivelycomprise at least one site of unsaturation. The oils principallycontemplated herein include what are normally referred to as thetriglyceride drying oils. The vegetable triglyceride drying oils includeplant oils and plant source-like synthetic and semi-synthetictriglycerides that can be transformed into hard, resinous materials [seeEncyclopedia of Polymer Science and Technology, H. F. Monk et al., eds.,John Wiley & Sons, (1966), pages 216-234]. The expression “drying oils”is generic to both true drying oils, which dry (harden) at normalatmospheric conditions, and semidrying oils, which must be baked atelevated temperatures in order to harden. Unless otherwise indicated,“drying oil” will be used herein in its broadest sense to refer to bothtypes of drying oil. The unsaturated fatty acids (linoleic or linolenic)of a drying or semidrying oil comprise double bonds that are readilyavailable for entering into an oxidative reaction, or other reactionsinvolved in the drying process. These oils may also include oleic fattyacids. Common sources of drying oils include cotton seed oil, castoroil, canola oil, linseed oil, oiticica oil, safflower oil, soybean oil,sunflower oil, corn oil, and tung oil. Of these oils, soybean oils ismost readily available in both its unmodified and epoxidized state, andis therefore the most preferred. The properties of the subjectindustrial lubricants can be tailored by blending together differentdrying oils.

In order to render oxidative stability to the aforementionedtriglyceride oils, it is essential that all, or substantially all (atleast about 90%, and preferably at least about 95%), of the sites ofunsaturation be modified by derivatization with a pair of short chainesters having a chain length in the range of C-2 to C-10, and preferablyin the range of C-4 to C-8. The modified oil is characterized by thefollowing formula:

-   -   wherein R, R′ and R″ are independently selected from C-7 to C-21        aliphatic fatty acid residues, each including the structures:    -   wherein R′″ is H or C-2 to C-10 straight or branched        hydrocarbon;    -   wherein the ratio of R″′=hydrocarbon:R″′=H in a given sample of        modified triglyceride is at least 90:10;    -   wherein m=0-1;    -   wherein n=0-3; and    -   wherein the average Σn for R, R′ and R″ in a given sample of        modified triglyceride is at least 1.

In most of the common vegetable oils listed above, the triglycerideesters are composed of C-18 fatty acids, and accordingly R, R′ and R″are C-17.

Vegetable oils have a tendency to form macro crystalline structures viaa uniform stacking of the ‘bent’ triacylglycerol backbone at lowtemperature. Such macro crystals restrict easy flow of the system due tothe loss of kinetic energy of individual molecules during self-stacking.The ester branching groups (R′″) not only serve to eliminate the sitesof unsaturation, but also impose spacing from other triglyceridemolecules, thereby interfering with the formation of macro crystallinestructures. The resultant modified triglycerides are characterized byenhanced fluidity, rendering them useful for the end-use applicationsenvisioned herein. Triglycerides that are merely hydrogenated for thepurpose of eliminating the sites of unsaturation will tend to harden atroom temperature due to alignment and stacking of adjacent molecules.For this reason, it is important that there be at least one site ofunsaturation available for derivatization that will yield two branchingsites. The ester side chains that are most effective for imposing thedesired molecular spacing and imparting the most desired pour pointproperties are those having a chain length of at least C6. However, thepour point and other functional properties of the derivatized oils arenot significantly increased when the C-7 to C-10 branching chains areused.

The triglyceride oil is first either partially or completely epoxidized.The resultant oxirane rings are then available for cross-linking.Epoxidation may be carried out as described by Qureshi et al. [PolymerScience and Technology, Vol. 17, Plenum Press, page 250] or by any othermethod as known in the art. The degree of epoxidation should be suchthat there is at least 1, and preferably at least 2 oxirane rings pertriglyceride molecule. Typically, the epoxidation is carried tocompletion. Epoxidized soybean oil, for example, would have 3-7 oxiranerings per molecule. Assuming complete conversion in the subsequentreaction(s), the value of n in Formula I, above, will coincide with thenumber of oxirane rings in the original epoxidized oil.

In what is described herein as the “one-step chemical modification” or“one step reaction scheme”, the epoxidized oil is reacted in a singlestep reaction with an appropriate anhydride to yield the desired diesterderivative. For the C-2 to C-10 diesters, the respective anhydrideswould be acetic, propionic, butyric, valeric, hexanoic (caproic),heptanoic, octanoic (caprylic), nonanoic (pelargonic) and n-decanoic(capric). Boron trifluride trifluoride etherate or other suitablecatalyst in an anhydrous solvent is used to simultaneously open theoxirane ring and activate the anhydride. At the completion of thereaction, the oxirane rings are quantitatively, or nearlyquantitatively, converted to the diester derivative. This reaction ispreferably conducted at elevated temperatures, usually exceeding about40° C. With boron trifluride trifluoride etherate as the catalyst, theoptimal conditions are 50° C. for about 3 hours.

In the two-step modification, the epoxidized oil is first refluxed in anaqueous solvent in the presence of a strong acid in order to hydrolyzethe oxirane ring to a dihydroxy intermediate. The ring opening ispredominantly the major reaction in this stage with minimal hydrolysisof the ester linkage. The retention of the triacylglycerol backbone isimportant for maintaining the biodegradability of the vegetable oil. Asuitable acid for this purpose is perchloric. The triacylglycerolstructure is largely preserved at temperatures less than 100° C. Thedihydroxy compound exhibits a noticeable increase in viscosity over theepoxidized oil due to hydrogen bonding through the —OH pair.

In the second step, the dihydroxy derivative is reacted with theappropriate anhydride to yield the diester. The second step may takeplace at room temperature. For both steps, a combination of time andtemperature is selected to insure that the reaction goes to completion,or nearly so (at least 90%). Both stages of the modification can becompleted in 48 hours or less.

Whether the modified triglycerides of this invention are produced by theone-step or two-step modification, it is important that the ratio ofdiester derivative (where R′″ is a C-2 to C-10 straight or branchedhydrocarbon) to total number of unreacted, precursor functional groups(dienes, oxirane rings, and dihydroxy groups) is at least about 90:10.

As previously indicated and as demonstrated in the Examples, below, themodified triglycerides of this invention have superior properties whichrender them useful as hydraulic fluids. Other potential uses of thesemodified triglycerides are as biodegradable base stocks for lubricantapplications, such as crankcase oils, drilling fluids, two-cycle engineoils, metal working fluids, wear resistant fluids, greases, and thelike. Certain of these modified triglycerides meet or exceed many, ifnot all, specifications for some lubricant end-use applications withoutthe inclusion of conventional additives. However, they may be formulatedwith other functional components, such as extreme-pressure additives,anti-wear additives, pour point depressants, other base stocks, diluentsand the like. Determination of the requisite amount of additive for aparticular application would be within the skill of a person in the art.

It is important for all of the end-use applications envisioned hereinthat the pour point of the subject modified triglycerides is below roomtemperature, and preferably below 0° C. As shown in the examples below,pour point temperatures as low as approximately −21° C. have beenattained for certain derivatives. It is also important that theoxidative stability is reduced as compared to that of the unmodifiedoil. The thin film micro-oxidation method, described further below,provides one measure of oxidative stability. The percent of insolubledeposit indicates the amount of insoluble oxidizable material in a givenoil. For example, the percent insoluble deposit for soybean oil isapproximately 65%. It is desirable for the products of the invention toexhibit a percent insoluble deposit of less than 30%, and preferablyless than 25%. Pressurized differential scanning calorimetry asdescribed in further detail, below, is another method for measuringoxidative stability. The start (T_(S)) and onset (T₀) temperatures ofoxidation obtained by this method are desirably higher than those forraw vegetable oil. T_(O) is defined as the temperature when rapidincrease in the rate of oxidation is observed in the system. Theoxidation start temperature (T_(S)) is the temperature during whichprimary oxidation products begin to form in the vegetable oil matrix.T_(S) is also an indication of loss of small molecular fragments due toevaporation.

The following examples are intended to further illustrate the invention,without any intent for the invention to be limited to the specificembodiments described therein.

EXAMPLE 1

Two-step Triglyceride Modification Synthesis of di-hydroxylated soybeanoil (di-OH-SBO) from epoxidized soybean oil (ESBO).

Epoxidized soybean oil (ESBO) was obtained from commercial sources(purity level of 98%) and was used without any further purification.Perchloric acid (HClO₄, 70%, ACS reagent) was used as a ring openingcatalyst.

The reaction was carried out by refluxing a 2450 ml aqueous solution of127.4 gm epoxidized soybean oil at 100° C. for 48 hours, in a three-neck5000 ml round bottom flask. Perchloric acid (26.05 gm) was addeddrop-wise to the reaction mixture that was constantly agitated by amechanical stirrer. After the reaction was complete, the mixture wascooled to room temperature and the organic phase was extracted withchloroform (CHCl₃) and washed three times with water to remove anytraces of acid remaining in the reaction mixture. The solvent wasremoved under reduced pressure at 80° C. and the product was storedunder dry vacuum overnight.

Synthesis of di-OHexanoyl-soybean oil (di-OHx-SBO) from di-hydroxylatedsoybean oil (di-OH-SBO).

Forty gm of di-OH-SBO was added to 40 gm of hexanoic anhydride in 1:1ratio, and 19.97 gm of pyridine in equimolar ratio was further added tothe reaction mixture. The mixture was stirred with a mechanical stirrerin a 500 ml glass round bottom flask for 48 hours at room temperature.Then the reaction solution was poured into ice water and again stirredfor 12 hours. The reaction mixture was extracted several times withsolvent diethyl ether. Then the organic phase was washed with 100 ml 3%HCl and 5% NaHCO₃ (each 3 times) and finally dried over anhydrous MgSO₄for 24 hours. The solvent was removed under reduced pressure at 80° C.and the product stored under vacuum.

Synthesis of di-OAcetoxy-soybean oil (di-OAc-SBO) from di-hydroxylatedsoybean oil (di-OH-SBO).

The procedure used for the production of di-OHx-SBO was repeated, exceptthat acetic anhydride was substituted for the hexanoic anhydride.

Synthesis of di-OButoxy-soybean oil (di-OBu-SBO) from di-hydroxylatedsoybean oil (di-OH-SBO).

The procedure used for the production of di-OHx-SBO was repeated, exceptthat butyric anhydride was substituted for the hexanoic anhydride.

EXAMPLE 2

One-step Triglyceride Modification Synthesis of di-OHexanoyl-soybean oil(di-OHx-SBO) from epoxidized soybean oil (ESBO).

In a dry three-neck 500 ml round bottom flask fitted with a condenserwere placed 50 gm of ESBO, 46.88 gm of hexanoic anhydride (1:1equivalent ratio) and 400 ml of methylene chloride (CH₂Cl₂). The mixturewas stirred and the temperature maintained at 50° C. under dry N₂atmosphere. Boron trifluride trifluoride etherate (BF₃ ether)(8-10drops) were added and the mixture was stirred and refluxed for 3 hours.After the reaction mixture cooled to the room temperature, it was washed3 times each with 5% NaHCO₃ solution followed by brine solution. Later,the mixture was dried over anhydrous magnesium sulfate (overnight). Itwas then filtered and evaporated under reduced pressure to recover thedi-OHx-SBO.

Molecular Analysis.

Products were subjected to NMR analysis to identify and compute therelative distribution of —CH_(n)— (n=0″3) carbons in the variousreaction products. NMR spectra (not shown) indicate that absorbance dueto epoxy group is absent in di-OH-SBO and di-OHx-SBO. The relativeintensity of terminal methyl group (δ 0.8-1.0 ppm) is significantlyhigher in di-OHx-SBO as compared to ESBO. The absence of the peak at δ1.4-1.55 ppm in di-OHx-SBO suggest that epoxy carbons of ESBO are nowthe branching sites for side chains in di-OHx-SBO.

The presence of functional groups were monitored using FTIR analysis.Absence of absorption at 822 cm⁻¹ due to the epoxy group indicates thatthe starting material undergoes complete ring opening with theconsequent generation of free —OH group resulting in dimeric (3550-3400cm⁻¹) and smaller amount of polymeric (3400-3200 cm⁻¹) associationthrough H-bonding.

Thin Film Micro-oxidation (TFMO) Method.

A small amount of oil (25pL) was oxidized under thin film conditions onan activated high carbon steel catalyst surface with a steady flow (20cm³/minute) of dry air passing over the heated sample. The oxidation wascarried out at constant temperature (175±1° C.) inside a bottomlessglass reactor. After a specified time length, the catalyst with theoxidized oil sample was removed from the oxidation chamber and cooledrapidly under a steady flow of dry N₂ and immediately transferred to adesiccator bottle. Later (approximately 2 hours), the catalyst wasweighed for sample loss due to evaporation (or gain due to oxidation)and then soaked (30 minutes) with tetrahydrofuran solvent to dissolvethe soluble portion of oxidized oil. The catalyst containing theinsoluble deposit was placed in a desiccator for complete removal oftrace solvent. After 2 hours, the catalyst samples were weighed todetermine the amount of insoluble deposit.

As shown in FIG. 1 the TFMO data reveals that epoxidation of, —C═C—bonds in SBO resulted in a product (ESBO) characterized by a lowinsoluble deposit until 1 hour into the oxidation process. Thereafter, asharp increase in the deposit formation suggests a catastrophicbreakdown of the epoxy group leading to oxidative polymerizationreaction through the reactive oxygen radical thus generated. Thepresence of branching in di-OHx-SBO lowers the initial thermal andoxidative stability of the oil as compared to ESBO (Table 1), howeverthe deposit-forming tendency remained fairly low and constant throughoutthe test.

Pressurized Differential Scanning Calorimetry (PDSC) method.

As a measure of oxidative stability, samples were subjected to PDSCusing a DSC 2910 thermal analyzer (Table 2, top). Nominally 1.5 mg ofsample was placed in a hermetically sealed type aluminum pan with apinhole lid for interaction of the sample with the reactant gas (dryair). A film thickness of less than 1 mm was required to ensure properoil-air interaction and eliminate any discrepancy in the result due togas diffusion limitations. Dry air (obtained commercially) waspressurized in the module at a constant pressure of 3450 KPa and thescanning rate was a constant 10° C./minute. The start (T_(S)) and onset(T₀) temperatures of oxidation were obtained from the reaction exothermin each case. T₀ is obtained from extrapolating the tangent drawn on thesteepest slope of reaction exotherm. High T₀ and T_(S) would suggest ahigh oxidative stability of the vegetable oil matrix.

Pour Point Method.

Pour points were determined by following the ASTM D 97 (1997) methodusing 50 ml samples. Temperatures were measured in 3° C. increments atthe top of the sample until it stopped pouring. Pour point values forSBO, ESBO, and each of the modified triglycerides are given in Table 3.The SBO has a pour point of −6° C., while ESBO freezes at 0° C. Thethermal and oxidative stabilities of ESBO due to the removal of —C═C—unsaturation, however, are at the expense of desirable fluidityproperties at cold temperatures. Attachment of at least a C-5 side chainat epoxy carbon sites improves the pour point significantly, asdemonstrated by the superior pour point for di-OHx-SBO (−18° C. to −21°C.).

EXAMPLE 3

Pour Point of di-OHx-SBO Formulations

Further improvement in the low temperature fluidity of di-OHx-SBO asprepared in Examples 1 and 2 was tested in a formulation comprising pourpoint depressant (PPD) additives, including sunflower oil, mineral oiland proprietary compounds (Table 4). Blending was carried out bystirring chemically modified oil with an optimized additive dose at roomtemperature for 2 hours. The purpose of the PPD additives was tosterically hinder crystallization of triacylglycerol molecules at lowtemperature bydisrupting the stacking mechanism. An optimum PPD additiveconcentration of 1% in the final blend enabled a pour point of −30° C.for di-OHx-SBO. Further addition of PPD additives made no significantimprovement in the pour point. Similarly, an optimized concentration of1% antioxidant (AO) additive (mixture of an alkylated phenol andproprietary compounds) was added to the final blend.

Oxidative stabilities of formulations containing diluent and diluentwith AO were determined by the PDSC method described in Example 1. Theresults are reported in Table 2 (bottom).

EXAMPLE 4

Low Temperature Storage Stability of di-OHx-SBO Formulations

The same experimental setup (ASTM D 97) as used for pour pointdetermination in Example 1 was adopted for low temperature stabilitymeasurements. The samples were kept at −25° C. and visually inspectedevery 24 hours for 7 days for fluidity (similar to pour pointdetermination). Failing criteria consisted of crystallization,solidification and formation of solid particles but did not includehaziness and loss of transparency.

The (di-OHx-SBO) formulated with PPD was susceptible to freezing whenheld for 3 days at −25° C. In order to improve the cold storagestability of the formulation over an extended time period, abiodegradable synthetic ester, dibutyl adipate (96% purity) wasuniformly blended into the formulation as a diluent at severalconcentrations. The final optimized formulation di-OHx-SBO+1% PPD+1%AO+diluent (70:30 oil:diluent ratio) that had a pour point of −42° C.passed the 7 days storage stability test at −25° C.

TABLE 1 Thin Film Micro Oxidation of Soybean Oil Modifications^(a) Testoils^(b) % Volatile loss % Insoluble deposit SBO 12.17 65.85 ESBO 7.029.53 OAc-SBO 12.09 9.14 OBu-SBO 28.02 15.07 di-OHx-SBO (2-step) 57.8328.33 di-OHx-SBO (1-step) 52.47 22.12 ^(a)Conducted at 175° C., 25 μL, 1h; ^(b)SBO = Soybean oil; ESBO = Epoxidized soybean oil; OAc-SBO =Acetoxy-SBO; OBu-SBO = Butoxy-SBO; di-OHx-SBO = Hexanoyl-SBO

TABLE 2 Pressurized Differential Scanning Calorimetry at 10° C./min TestStart temperature Onset temperature oils^(a) (T_(s)) ° C. (T_(o)) ° C.SBO 161.3 178.2 ESBO 177.4 203.9 OAc-SBO 135.7 165.1 OBu-SBO 140.1 170.2di-OHx-SBO (2-step) 171.9 196.6 di-OHx-SBO (1-step) 173.7 196.3Formulations: di-OHx-SBO (2-step):diluent 172.9 194.5 (70:30) di-OHx-SBO(2-step):diluent 201.1 215.2 (70:30) + additive (1% AO) ^(a)SBO =Soybean oil; ESBO = Epoxidized soybean oil; OAc-SBO = Acetoxy-SBO;OBu-SBO = Butoxy-SBO; di-OHx-SBO = Hexanoyl-SBO; AO = Antioxidant

TABLE 3 Pour Points^(a) of Soybean Oil Modifications Test oils^(b) Pourpoint (° C.) SBO −6 ESBO 0 OAc-SBO −3 OBu-SBO −3 di-OHx-SBO (2-step) −18di-OHx-SBO (1-step) −21 ^(a)ASTM D 97; ^(b)SBO = Soybean oil; ESBO =Epoxidized soybean oil; OAc-SBO = Acetoxy-SBO; OBu-SBO = Butoxy-SBO;di-OHx-SBO = Hexanoyl-SBO

TABLE 4 Pour Points^(a) of di-OHx-SBO Formulations Test PPD^(c)Diluent:oil Pour point oil^(b) (%) (ratio) (° C.) di-OHx-SBO 0 0:100 −18(2-step) di-OHx-SBO 1 0:100 −30 (2-step) di-OHx-SBO 1 30:70  −42(2-step) di-OHx-SBO 2 40:60  −45 (1-step) ^(a)ASTM D 97; ^(b)di-OHx-SBO= Hexanoyl-SBO; ^(c)PPD = Pour point depressant

1. A modified vegetable triglyceride characterized by the followingformula:

wherein R, R′ and R″ are independently selected from C-7 to C-21aliphatic fatty acid residues, each including the structures:

wherein R′″ is H or C-2 to C-10 straight chain or branched hydrocarbon;wherein the ratio of R′″=hydrocarbon:R″′=H in said modified triglycerideis at least 90:10; wherein m=0-1; wherein n=0-3; and wherein the averageΣn for R, R′ and R″ in said modified triglyceride is at least
 1. 2. Themodified vegetable triglyceride of claim 1, wherein R, R′ and R″ areC-17 aliphatic fatty acid residues.
 3. The modified vegetabletriglyceride of claim 1, wherein the average Σn for R, R′ and R″ in saidmodified triglyceride is at least
 3. 4. The modified vegetabletriglyceride of claim 1, wherein the average Σn for R, R′ and R″ in saidmodified triglyceride is in the range of 3-7.
 5. The modified vegetabletriglyceride of claim 1, wherein R′″ is a C-4 to C-8 straight chainhydrocarbon.
 6. The modified vegetable triglyceride of claim 1, whereinR′″ is a C-6 straight chain hydrocarbon.
 7. The modified vegetabletriglyceride of claim 1, wherein m=1.
 8. A modified vegetabletriglyceride of claim 1, wherein said vegetable triglyceride is selectedfrom the group consisting of cotton seed oil, castor oil, canola oil,linseed oil, oiticica oil, safflower oil, soybean oil, sunflower oil,corn oil, and tung oil.
 9. A modified vegetable triglyceride of claim 1,wherein said vegetable triglyceride is soybean oil.
 10. A method forpreparing a modified vegetable triglyceride characterized by thefollowing formula:

wherein R, R′ and R″ are independently selected from C-7 to C-21aliphatic fatty acid residues, each including the structures:

wherein R′″ is H or C-2 to C-10 straight chain or branched hydrocarbon;wherein the ratio of R″′=hydrocarbon:R″′=H in said modified triglycerideis at least 90:10; wherein m=0-1; wherein n=0-3; and wherein the averageΣn for R, R′ and R″ in said modified triglyceride is at least 1; themethod comprising reacting an epoxidized vegetable triglyceride havingat least one oxirane ring structure with an anhydride selected from thegroup consisting of acetic, propionic, butyric, valeric, hexanoic,heptanoic, octanoic, nonanoic and n-decanoic in the presence of asuitable catalyst for simultaneously opening the oxirane ring andactivating the anhydride in order to convert each of said oxirane ringstructures to a diester derivative.
 11. The method of claim 10, whereinsaid catalyst is boron trifluride etherate.
 12. The method of claim 11,wherein said reacting takes place a temperature of at least 40° C. 13.The method of claim 10, wherein said epoxidized vegetable triglycerideis epoxidized soybean oil.
 14. The method of claim 10, wherein saidanhydride is hexanoic anhydride.
 15. A method for preparing a modifiedvegetable triglyceride characterized by the following formula:

wherein R, R′ and R″ are independently selected from C-7 to C-21aliphatic fatty acid residues, each including the structures:

wherein R′″ is H or C-2 to C-10 straight chain or branched hydrocarbon;wherein the ratio of R′″=hydrocarbon:R′″=H in said modified triglycerideis at least 90:10; wherein m=0″1; wherein n=0″3; and wherein the averageΣn for R, R′ and R″ in said modified triglyceride is at least 1; themethod comprising: a. refluxing an epoxidized vegetable triglyceridehaving oxirane ring structures in an aqueous solvent in the presence ofa strong acid catalyst in order to hydrolyze the oxirane ring to adihydroxy intermediate; b. reacting said dihydroxy intermediate with ananhydride selected from the group consisting of acetic, propionic,butyric, valeric, hexanoic, heptanoic, octanoic, nonanoic and n-decanoicin order to covert said dihydroxy intermediate to a diester derivative.16. The method of claim 15, wherein said catalyst is perchloric acid.17. The method of claim 15, wherein said refluxing in step (a) isconducted at approximately 100° C.
 18. The method of claim 15, whereinsaid reacting in step (b) is conducted at room temperature.
 19. Themethod of claim 15, wherein said epoxidized vegetable triglyceride isepoxidized soybean oil.
 20. The method of claim 15 wherein saidanhydride is hexanoic anhydride.
 21. An industrial fluid comprising themodified vegetable triglyceride of claim 1 and another functionalcomponent.
 22. The industrial fluid of claim 21, wherein said functionalcomponent is selected from the group consisting of extreme-pressureadditive, anti-wear additive, pour point depressant, base stock, anddiluent.